code: def get_distribution(GC_fraction):
      from simdna.util import DiscreteDistribution
  
      return DiscreteDistribution(
          {
              "A": (1 - GC_fraction) / 2,
              "C": GC_fraction / 2,
              "G": GC_fraction / 2,
              "T": (1 - GC_fraction) / 2,
          }
      )
  
file_path: deepchem/deepchem/molnet/dnasim.py
imports: import numpy
label_desc: Use image node_id 1 for calling a global function with example usage: get_distribution(GC_fraction) and returns: DiscreteDistribution